Autodrilling control with annulus pressure modification of differential pressure

Abstract

A control system that corrects differential pressure measurements with downhole annulus pressure information is disclosed. When differential pressure is zeroed with the BHA off-bottom, the annulus pressure value is baselined. During drilling, a controller receives surface differential pressure measurements and annulus pressure measurements. As the controller receives each new annulus pressure measurement, it compares it to the baseline annulus pressure value to obtain a different annulus pressure value. The controller corrects the surface differential pressure measurements with the annulus pressure measurements. As the controller receives each new surface differential pressure measurement, it subtracts out the current difference annulus pressure value. As a result, the modified surface differential pressure measurement remains a reflection of mud motor performance that removes the influence of the increased density of the fluid, thereby improving autodrilling control. The modified surface differential pressure measurements are also used to determine mud motor torque.

What is claimed is: 
     
       1. An apparatus, comprising:
 a transceiver configured to:
 receive a differential pressure measurement of a mud flow in a drilling rig from a differential pressure sensor; and 
 receive an annulus pressure measurement of pressure in a vicinity to a bottom hole assembly of the drilling rig from an annulus pressure sensor; and 
 
 a controller configured to:
 receive the differential pressure measurement and the annulus pressure measurement from the transceiver; 
 modify the differential pressure measurement with the annulus pressure measurement; and 
 control a rate of penetration of the bottom hole assembly with the modified differential pressure measurement. 
 
 
     
     
       2. The apparatus of  claim 1 , wherein the controller is further configured to:
 establish a baseline annulus pressure from a concurrent annulus pressure measurement taken by the annulus pressure sensor at approximately a same time as differential pressure is zeroed with the bottom hole assembly off-bottom. 
 
     
     
       3. The apparatus of  claim 2 , wherein the controller is further configured to:
 subtract the annulus pressure measurement from the baseline annulus pressure to obtain a delta annulus pressure measurement; and 
 modify the differential pressure measurement with the delta annulus pressure measurement to obtain the modified differential pressure measurement. 
 
     
     
       4. The apparatus of  claim 1 , wherein the controller is further configured to subtract the annulus pressure measurement from the differential pressure measurement to obtain the modified differential pressure measurement. 
     
     
       5. The apparatus of  claim 1 , wherein the apparatus comprises an autodriller. 
     
     
       6. The apparatus of  claim 1 , wherein:
 the transceiver receives differential pressure measurements at a first frequency, 
 the transceiver receives annulus pressure measurements at a second frequency, and 
 the first frequency is greater than the second frequency. 
 
     
     
       7. The apparatus of  claim 1 , wherein the controller is further configured to:
 re-establish a baseline annulus pressure from a current annulus pressure measurement in response to the bottom hole assembly coming off-bottom and differential pressure being re-zeroed. 
 
     
     
       8. A method, comprising:
 receiving, at a controller of a drilling rig from a differential pressure sensor, a differential pressure measurement of a mud flow in the drilling rig; 
 receiving, at the controller from an annulus pressure sensor, an annulus pressure measurement from fluid in a vicinity to a bottom hole assembly of the drilling rig; 
 modifying, by the controller, the differential pressure measurement with the annulus pressure measurement; and 
 controlling, by the controller, a rate of penetration of the bottom hole assembly with the modified differential pressure measurement. 
 
     
     
       9. The method of  claim 8 , further comprising:
 zeroing, by the controller, a differential pressure as the bottom hole assembly is off-bottom prior to commencing drilling operations; and 
 establishing, by the controller in response to the zeroing, a baseline annulus pressure from a concurrent annulus pressure measurement taken by the annulus pressure sensor. 
 
     
     
       10. The method of  claim 9 , wherein the modifying further comprises:
 subtracting, by the controller, the annulus pressure measurement from the baseline annulus pressure to obtain a delta annulus pressure measurement; and 
 modifying, by the controller, the differential pressure measurement with the delta annulus pressure measurement to obtain the modified differential pressure measurement. 
 
     
     
       11. The method of  claim 8 , wherein the modifying further comprises:
 subtracting, by the controller, the annulus pressure measurement from the differential pressure measurement to obtain the modified differential pressure measurement. 
 
     
     
       12. The method of  claim 8 , wherein:
 the receiving the differential pressure measurement comprises receiving the differential pressure measurement at a first frequency, 
 the receiving the annulus pressure measurement comprises receiving the annulus pressure measurement at a second frequency, and 
 the first frequency is greater than the second frequency. 
 
     
     
       13. The method of  claim 8 , further comprising:
 re-zeroing, by the controller, a differential pressure against which the differential pressure measurement is compared in response to the bottom hole assembly coming off-bottom; and 
 re-establishing, by the controller in response to the re-zeroing, a baseline annulus pressure. 
 
     
     
       14. The method of  claim 8 , further comprising:
 deriving, by the controller, a mechanical specific energy value based on the modified differential pressure measurement. 
 
     
     
       15. A non-transitory machine-readable medium having stored thereon machine-readable instructions executable to cause a machine to perform operations comprising:
 receiving a differential pressure measurement of a mud flow in a drilling rig from a differential pressure sensor; 
 modifying the differential pressure measurement with an annulus pressure measurement of pressure in a vicinity to a bottom hole assembly of the drilling rig received from an annulus pressure sensor; and 
 controlling a rate of penetration of the bottom hole assembly into a subterranean formation with the modified differential pressure measurement. 
 
     
     
       16. The non-transitory machine-readable medium of  claim 15 , wherein the annulus pressure measurement comprises a first annulus pressure measurement, the operations further comprising:
 receiving a first plurality of differential pressure measurements including the differential pressure measurement; and 
 modifying the first plurality of differential pressure measurements with the first annulus pressure measurement. 
 
     
     
       17. The non-transitory machine-readable medium of  claim 16 , the operations further comprising:
 receiving a second annulus pressure measurement from the annulus pressure sensor; 
 receiving a second plurality of differential pressure measurements after the first plurality of differential pressure measurements; and 
 modifying the second plurality of differential pressure measurements with the second annulus pressure measurement. 
 
     
     
       18. The non-transitory machine-readable medium of  claim 15 , the operations further comprising:
 zeroing a differential pressure as the bottom hole assembly is off-bottom prior to commencing drilling operations; and 
 establishing, in response to the zeroing, a baseline annulus pressure from a annulus pressure measurement concurrent to the zeroing taken by the annulus pressure sensor. 
 
     
     
       19. The non-transitory machine-readable medium of  claim 18 , wherein the modifying further includes operations comprising:
 subtracting the annulus pressure measurement from the baseline annulus pressure to obtain a delta annulus pressure measurement; and 
 modifying the differential pressure measurement with the delta annulus pressure measurement to obtain the modified differential pressure measurement. 
 
     
     
       20. The non-transitory machine-readable medium of  claim 15 , wherein the modifying further includes operations comprising:
 subtracting the annulus pressure measurement from the differential pressure measurement to obtain the modified differential pressure measurement.